Septic tank



Oct. 4, 1949. i P. N. SITTON 2,43,564

SEPTIC TANK Filed May 26, 194s Patented Oct. 4, 1949 UNITED" STATES PATEN SEPTIC TANK Philip N. Sitton, Dayton, Ohio Application May 26, 1948, Serial 'No. 29,261

This invention relates to septic tanks, and particularly to a specific improved form of aseptic tank by which an improved action is obtained in the tank and the life of the tank is increased. By life ofthe tank is meant the time between cleanings; these being required periodically.

The usual type of septic tank is either round, square, or rectangular. Tanks of this nature havehavenot been satisfactory for the reason that no thought has been given to the retention period and to sludge formationin the tank. To provide for an-eificient septictank it is essential that the retention period shall not be less than twenty-four hours. Also, to have a tank having any length of useful life, it is essential thatsludge formation shall be uniform over the bottom of the tank, eliminate piling up in the tank which reduces the retention period in the tank.

An object of this invention is to provide a septic tank which will have a satisfactory retention period, and in which sludge formation will be uniform over the bottom of the tank.

To accomplish the foregoing objects, it is a further object of the invention toprovide a septic tank that is substantially elliptical in transverse cross-section and in which the inner walls of the tank are in the form of a continuous are from the ends of the tank toward the middle thereof.

It is still another object of the invention to provide a septic tank that is fully portable and will have great strength against crushing by ground pressure when installed in the ground.

Further objects and advantages will become apparent from the drawings and the following description.

In the drawings:

Figure 1 is a perspective elevational view, partially in cross-section, of a concrete septic tank constructed in accordance with this invention;

Figure 2 is a plan View of the septic tank illustrated in Figure 1 but with the top cover removed;

Figure 3 is a perspective view of a portion of the septic tank illustrating the inlet bafile arrangement that is placed within the tank;

Figure 4 is a perspective view of a portion of the septic tank illustratin the arrangement of the outlet bafile in the tank.

In this invention the septic tank l consists of three principal sections I I, I2 and I3 which are cast of concrete. Each section II, I2 and I3 has the same general contour of the vertical side wall section thereof, which is illustrated in Figure 2. The general form of the tank, particularly the 1 Claim. (Cl. 2106).

inner wall thereof; is in the naturerof an ellipse, as shown in Figure 2. v

The tank It) has a bottom or base slab l4. upon which the lower section II is placed. -The two side wall sections I2 and I3 are then placed upon the section II to provide a tank of suificient depth to give the desired capacity;

The section i3 is provided with an inlet opening l5 at one end thereof and an outlet opening it at the opposite end thereof. It will be noted that the inlet and outlet openings are in sub stantially the end extremity of the elliptical form of the septic tank, thus placing the inlet and outlet at the points of greatest separation.

A baflle I1 is provided adjacent the inlet opening IE to force the efiluent to pass downwardly into the tank. This bafile I! is provided with ears l8 at opposite sides thereof which are insertedin suitable slots I9 in the side wall of the section l3 to support bafile I1 in its position adjacent the inlet opening l5.

A baille 20 is positioned adjacent theoutlet opening l6 and may be supported bythe side walls of the section l3 in the same manner as the inletbafiiell. ,7

It will be noted that the inlet baffie l 1 provides, with the side wall of theseptic tank, a gradually increasing chamber from the inlet opening l5 toward. the interior of the tank. This arrangement provides for gradual spread of the effluent. uni formly throughout the tank.

A top cover 25 is provided for the septic tank and mayconsist of a plurality'of sections 25a each of which is provided with an'iron loop 26 for raising the lid off the tank.

The inner wall 27 of the septic tank is in the form of a continuous curve from one end of the tank toward the middle portion thereof to provide a smooth-flowing wall portion. The are of curvature of the inner wall 2'! of the septic tank continuously decreases from the ends of the tank toward the center portion thereof with the center portion of the tank being provided with the minimum arc of curvature and the end portions of the tank with the maximum arc of curvature. Thus, the inner wall 21 of the tank is in the form of an ellipse.

It was discovered after much inspection of hundreds of tanks, that the flow pattern of the efliuent through the tank is in the form of an ellipse regardless of the shape of the tank. Also, that to provide for a desired retention period of approximately twenty-four hours within the tank, it was necessary to have the tank at least twice as long as wide. Such an arrangement 7 could be provided in a rectangular tank, but

sludge would tend to pile up at the inlet end of this kind of a tank for the reason that the flow pattern of the eiiluent could not form naturally within the tank. The disturbance to the flow pattern prevents uniform distribution of sludge over the bottom of the tank, thus greatly reducing the life of the tank and also reducing the retention periodof the matter within the tank.

The smooth elliptical .iorm oisepticgz-tankepro- 10 'vides maximum efl'iciency for the'fiow pattern of the eflluent can be formed naturally and will be, continuously maintained without any disturb ance. Since the elliptical form of the innemwall; 21 of the septic tank allows the eflluent to now, in its natural flow pattern throughthe-'-tank" from the inlet to the outlet thergoigguniiqrm dis-w tribution of sludge is obtained over the bottom of the tank. This uniform distributiorrdsalsoaided by the fact that=the elliptical form of the tanki'eause'skthe'seflluent at the-inlet 281111 170 move at a slightly greater rate thanlwhen itapproaches thmcenter. I portionaioi ithe; tank .'Ihus-,. sludge is canrizdi-away iromathei inlet-endiofv'theutankzand theiusual pilin'g'i up of= sludge is i avoided:- ate the inltsend of; the tankn The elliptical 'vformi of theseptic. tank has-:also beemiound-to bEi-most adapted for installation of concrete: tanks underground for makimum st engttx isgiven to the tank to='=prevoentcollapse against groundmressurea "When avseptic tank is installed underground, the: ground applies considerable-pressure upon the walls of the' septic tankI- pressure shifts from time-{to tim e due to varyingconditionsof the ground, such 'as the water content of the ground or freezin'g and thawing'eonditionsi Since all-j'pertions-ofthe ellipticai tank-aredn the form of an 'ard maximum strengtlnis given-to the wall section-3 Thus, it has been found that the iwall sectlon of the tank=ican be -greatly -reduced from that offponventional -concrete-septic tanks-to such an eitent that only about' of-the thickness7of wall is required, compared to that normally recommended for underground storage tank's;; As

ffl fiexample; the wall 'ofthe septic tankof this invention =is- -approximatelyj 2""whereas xecommendations for 1 undergroundf'storage "tanks. spa;- cify walrthiokness'ofifrom 41 toi5":" Thus; the form of the septic tankfaids -greatly'fin' portability of;the device-for installation in theground;

Having thus' fullydescribed'my'imcention; what 4 I claim as new and desire to secure by Letters Patent is:

A septic tank consisting of, a bottom wall, vertically arranged side wall means forming a hollow body providing an unobstructed elliptical chamber of the same size from top to bottom thereof having an internal length substantially twice that of the internal width thereof with the maximum width of the chamber being midway between opposite ends of :the chamben-an inlet and an outlet'in saidside wall means adjacent the upper edge thereof and positioned in the end extremities of the said chamber, said chamber .having the inner wall thereof forming an ellipse at all transverse cross-sections of the chamber from top to bottom thereof against which said mn-QIEWBIIL fluidamove in a continuously expanding flow across said chamber from said inlet end thereof to the median portion of said chamber and in a continuously contracting flow from the said medianrportiongof said chamben-tosaid-outlet end thereof, said innerrwall, at ,bothlsides of the -chamberhaving a continuous .arcof. curyae ture that ,continuously decreases -fromeach: end Ofuthfl chamber toward the .center portion-thereof with the centerportlons-of the-innercwalls form ing.- the- -minimumarcuate. portions andntheiend portionslformingi the maximum, arcuategportions, and bafileqmeans extending across. ,said elliptical chamberinto engagementwith saidiarcuate' walls thereof at each endm ithe ichambersadjacentthe inlet and. outlet .andextending. from ai position above. the respective .levels of saidinletand outlet openings to: a .position. below the ,respective. levels of saidinlet and outlet openings.

- ,SITTON;

REFERENCES'LBITEDI UNITED. STATES"PATENTS 7 Number Name -Date-sz 1 ?,5231 Hahn .Oct- 3,-1925 1,634,871 Heple-r; July,- 5,-;192'Z 1,695,78-1-. Otis. -i Deer-$18,119.28 1',87-7,5 07;- Hendricks .Sept. :13, 1932 2,378,616 Burgettg--. June; 19, 19,45 ZAfilQfiZGZE; Sitton May ;4,21,948

FOREIGNPATENTS Number Country Date 645,5 l0; France June 27., 1928 30.6492.

Germany June .22) .1918 

